1. Field of Invention
This invention generally relates to a patch for dispensing parenteral fluid medication through the skin and more particularly to a patch which has its regimen electronically controlled by timing and by sensors.
In general patches have found usage for the ambulatory patient requiring an extended regimen of a single drug such as for a chronic condition or for birth control.
Microchip control of drug dispensing and physiological sensing is now used in hospital ICUs. As these technologies are downsized and move to ambulatory patient devices, the microchip processing evolves for a transdermal system that is worn to control a chronic condition but that will also respond to trauma. Such a multi-response transdermal system requires a multi-drug transdermal patch that allows discretionary, independent selection of drug, sequence, and potency.
Chronic conditions such as hormone deficiency which rely on continuous medication would benefit from a transdermal regimen which was moderated to daily and weekly biorythyms. Other chronic conditions such as diabetes, panic, or pain attacks may require intermittent administration to match severity and duration. Other conditions such as cardiovascular may require selection and sequencing from a variety of drugs to counter the precise nature of an attack.
Non-medical situations may require multiple doses during the operational life of a transdermal patch. An example of this would be a commercial pilot who may require a stimulant at intervals during a long flight to remain alert, based on physiological sensing.
2. Description of the Prior Art
Drug Selection: There are two branches to prior art on multiple reservoir transdermal dispensing: (1) those patches that have multiple reservoirs but simultaneously dispense from all their reservoirs such as Reller, and (2) patches that offer drug selectivity. 8 External selection includes (1) injection into the patch by Jacobsen and by Mathiesen, (2) selection by reservoir replacement by Newman and by Sabalis, and (3) selection by a central controller from multiple patches with differing drugs by Newman. There are two branches to prior art on selective multi-drug transdermal dispensing: (1) passive migration by diffusion, dilution, or migration such as Helber, and (2) assisted migration by electrophoteresis and electroosmosis such as Sibalis in #4,921,475.
Because of the need for uniform transfer over the exposed skin area, electrophoteresis requires complex electrode arrangements that have not addressed multi-drug selection.
Helber is a manual unit and despite its selection capability has no provision for electronic control.
Both passive and assisted migration are inefficient from a space standpoint and are not likely to be able to accommodate more than a few drugs per patch.
Sequence Selection: All prior art discloses predetermined sequencing. None disclose variable sequencing.
Dosage Rate Selection: User activated systems such as Helber et al provide only continuous medication after activation. Helber et al states in line 35 that "only a single release rate results per system."
Electrophoteric systems are capable of varying the dosage level by varying the electrical characteristics. However, true multi-drug responsive systems must be capable of dispensing mixture of drugs with differing size molecules and sensing the pharmacokinetic reactions and modifying the administration to respond perhaps by more aggressive therapy. This implies a reselection of drug and regimen, a response not possible in the prior art.
Prior art on graduated delivery of medication include electrophoteric systems, multi-polymer, and rate-limited membrane systems. Only the electrophoteric system is compliant to varying patient needs in a microchip controlled environment. Prior systems possessed no positive dispensing capability. Their electrodes were placed within each reservoir to assist migration such as Reller. No common reservoir or common electrode was possible. This lack make for a complex system limited in the number of drugs that could be efficiently administered.
None of these systems has a zero level of medication when the drug laden patch is attached except Hebler.
None of these systems features medication dispensing internal to the patch to allow variation in drug choice and concentration, which controls release rate.